Link pgbouncer dynamically (#10749)

I don't see the point of static linking, postgres itself and many of the
extensions are already built dynamically.

One reason for the change is that I'm working on bigger changes to start
using systemd in the compute, and as part of that I wanted to add the
--with-systemd configure option to pgbouncer, and there doesn't seem to
be a static version of libsystemd (at least not on Debian).

compute/compute-node.Dockerfile

@@ -1615,7 +1615,7 @@ RUN set -e \
     && git clone --recurse-submodules --depth 1 --branch ${PGBOUNCER_TAG} https://github.com/pgbouncer/pgbouncer.git pgbouncer \
     && cd pgbouncer \
     && ./autogen.sh \
-    && LDFLAGS=-static ./configure --prefix=/usr/local/pgbouncer --without-openssl \
+    && ./configure --prefix=/usr/local/pgbouncer --without-openssl \
     && make -j $(nproc) dist_man_MANS= \
     && make install dist_man_MANS=
 
@@ -1824,6 +1824,7 @@ RUN mkdir /usr/local/download_extensions && chown -R postgres:postgres /usr/loca
 # libzstd1 for zstd
 # libboost* for rdkit
 # ca-certificates for communicating with s3 by compute_ctl
+# libevent for pgbouncer
 
 RUN echo 'Acquire::Retries "5";' > /etc/apt/apt.conf.d/80-retries && \
     echo -e "retry_connrefused = on\ntimeout=15\ntries=5\n" > /root/.wgetrc
@@ -1862,6 +1863,7 @@ RUN apt update && \
         libxslt1.1 \
         libzstd1 \
         libcurl4 \
+        libevent-2.1-7 \
         locales \
         procps \
         ca-certificates \